Chemical mechanical planarization (CMP) is used extensively in the manufacture of semiconductors. During a CMP process, material is removed from a wafer substrate by the action of a polishing pad, a polishing slurry, and optionally chemical reagents. Over time, the polishing pad becomes matted and filled with debris from the CMP process. Periodically, the polishing pad is reconditioned using a pad conditioner that abrades the polishing pad surface and opens pores and creates asperities on the surfaces of the polishing pad. The function of the pad conditioner is to maintain the removal rate in the CMP process.
CMP represents a major production cost in the manufacture of semiconductor and memory devices. These CMP costs include those associated with polishing pads, polishing slurries, pad conditioning disks and a variety of CMP parts that become worn during the planarizing and polishing operations. Additional cost for the CMP process includes tool downtime in order to replace the polishing pad and the cost of the test wafers to recalibrate the CMP polishing pad.
A typical polishing pad comprises closed-cell polyurethane foam. During pad conditioning, the pads are subjected to mechanical abrasion in order to physically cut through the cellular layers of the pad surface. The exposed surface of the polishing pad contains open cells, which traps debris such as spent polishing slurry and material removed from the wafer during the CMP process. In each subsequent pad-conditioning step, the pad conditioner removes the outer layer of cells containing the embedded materials and minimizes removal of layers below the outer layer. Over-texturing of the polishing pad results in a shortened life, while under-texturing results in insufficient material removal rate and lack of wafer uniformity during the CMP step.
There is a continuing need for CMP pad conditioners with improved CMP pad texturing capabilities that enhances removal of debris for better controlled pad cut rate, without excessive removal of material from the polishing pad.